PERTH Scotland (Reuters) - Scottish nationalist leader Alex Salmond implored Scots to grasp the 'opportunity of a lifetime' to secure independence in a vote on Thursday that could break the United Kingdom apart.

"This is our opportunity of a lifetime and we must seize it with both hands," Salmond told a meeting of supporters in Perth, eastern Scotland, just hours before polling stations open.

"This in my estimation has been the greatest campaign in Scottish democratic history," Salmond said, though he added that the British establishment had thrown "the kitchen sink" at the independence campaign.

He derided an offer of more powers from British leaders as a "tepid offer of next to nothing" but said he would accept the result if he lost the independence vote.

"Scotland's future must be in Scotland's hands," Salmond told hundreds of supporters waving the white on blue Scottish flag who chanted "Yes we can".